The present invention relates to acoustic attenuating liners. More particularly, the invention relates to a method of making an acoustic attenuating liner.
Acoustic attenuating liners are widely used for attenuating noise produced by the jet engines of aircraft. It is well known in the art to make an acoustic attenuating liner or panel having a sound reflecting solid back plate, a perforated metal face plate and a honeycomb or cellular core between such plates to partition the air into a multiplicity of separate cells. However, the acoustic attenuating liners are deficient for certain applications, due to inadequacies of the face plate. Thus, the metals used in the construction of these liners are prone to corrosion, thereby resulting in the loss of effectiveness and the need for periodic replacement. Furthermore, the holes formed through the face plate may be too large in diameter and/or spaced too far from each other for effective sound attenuation.
The principal object of the invention is to provide a method of manufacturing a new and improved acoustic attenuating liner.
An object of the invention is to provide a method of manufacture of a face plate of an acoustic attenuating liner, which face plate is corrosion-proof and has a desired or specified porosity.
Another object of the invention is to provide a method of making a face plate of an acoustic attenuating liner, which consists of laser drilling holes through said plate whereby the diameter of the holes and the spacing between next-adjacent holes may be made as small as desired thereby to meet the specific flow resistances.